Is accidentally stuck with a needle or other sharp item
that is contaminated with HIV.

HIV may be spread more easily
in the early
stage of infection and again
later, when symptoms of HIV-related illness develop.

A woman who is infected
with HIV can spread the virus to her baby during pregnancy, delivery, or
breast-feeding.

How HIV is not spread

The virus doesn't survive well outside the body. So HIV cannot be spread through casual contact with an infected person, such as
by sharing drinking glasses, by casual kissing, or by coming into contact with the person's sweat or urine.

It is now extremely rare in the United States for HIV to
be transmitted by
blood transfusions or organ transplants.

The window period

After you've been infected, it can take 2 weeks to 6 months for your body to start making HIV antibodies.

This means that during this time you could have a negative HIV test, even though you have been infected and can spread the virus to others.

Stages of HIV

Most people go through the following
stages after being infected with HIV:

Initial stage (stage 1)

The first stage of HIV infection is defined by the U.S. Centers for Disease Control and Prevention (CDC) as a CD4+ cell count of at least 500 cells per microliter or a percentage of CD4+ cells at least 29% of all
lymphocytes. People in this stage don't have any symptoms.3

Chronic stage (stage 2)

The second stage of HIV infection is defined by the CDC as a CD4+ cell count of 200
to 499 or a percentage of CD4+ cells of 14% to 28%.3 It may take years for HIV symptoms
to develop during this stage. But even though no symptoms are present, the virus is making copies of itself (multiplying) in the body during this time.

HIV multiplies so
quickly that the
immune system can't destroy the virus. After years of
fighting HIV, the immune system starts to weaken.

AIDS (stage 3)

AIDS occurs when the CD4+ cell counts drop below 200, the percentage of CD4+ cells is less than 14%, or an AIDS-defining condition is present.4

If HIV isn't treated, most people get
AIDS within 10 to 12 years after the initial infection.
With treatment for HIV, the progression to AIDS may be delayed or
prevented.

A small number of people who are infected with HIV are
rapid progressors. They develop AIDS within a few years if they don't get treatment. It is not known why the infection progresses faster in these
people.

Left
untreated, AIDS is often fatal within 18 to 24 months after it develops. Death
may occur sooner in people who
rapidly progress through the stages of HIV or in young
children.

Nonprogressors and people who are HIV-resistant

A few people have
HIV that doesn't progress to more severe symptoms or disease. They are
referred to as
nonprogressors.

A small number of people
never become infected with HIV despite years of exposure to the virus. These
people are said to be
HIV-resistant.